This invention pertains to a plug for a pier hole. More particularly, this invention relates to an inflatable plugging device for use in obstructing a hole drilled in the soil to be filled with concrete in the process of forming a pier.
Various types of expansible devices for plugging pipes, pipelines, tubes, well casings or other hollow conduits have been described in the patent literature. For example, U.S. Pat. Nos. 4,160,464 to Ballinger; 4,377,184 to Vetter; 4,398,565 to Williamson; 4,506,706 to Sandmann; 4,609,042 to Broadus; 4,612,961 to Vetter; and 4,614,206 to Mathison et al disclose different structures of such devices. In addition, U.S. Pat. No. 4,029,128 to Yamagishi decloses an air bag for plugging the hollow of a concrete pile driven into the ground with concrete material to be placed on top of the bag; and U.S. Pat. No. 4,660,644 to Egnor describes an elongated inflatable device having two spherically shaped ends with a recess therebetween for use in closing a blasting hole.
While the above-mentioned patents disclose the general concept of air-inflatable plugging devices designed for a variety of uses, the present invention provides a new approach for a structural form of an inflatable plug developed especially for use in conjunction with empty pier holes drilled in the soil which offers certain advantages over the prior art devices.
With a marked increase in the number of new residential homes, apartment complexes, condominiums and commercial buildings under construction on various types of soil, it has become increasingly desirable or frequently required, especially in earthquake-prone areas, to install a number of spaced apart concrete piers in vertically oriented holes drilled in the ground of the construction site in order to reinforce the foundation of the structure to be built thereon, to stabilize the soil and to level the ground when the need arises. Although the depth of pier holes is usually in the range of from 6 to 30 feet, it may vary broadly between about 2 and 50 feet depending on the character of the house or the building. Likewise, the diameter of such holes may vary between about 6 and 60 inches, although usually between 12 and 36 inches. As it is highly important that the interior of drilled holes remains uncontaminated by foreign materials which may fall therein before a concrete mixture is poured in, the holes are frequently covered with plywood sheets to prevent entry of such undesirable materials therein. However, such practice has been found not very satisfactory, as plywood covers may inadvertendly be displaced so as to expose a portion or the entire opening of the hole. Moreover, a partially or entirely open pier holes on a building site presents a potential danger of accidental fall of a person or an animal therein. Thus the present invention overcomes the disadvantages of the current practice of covering pier holes with plywood sheets.